The letters in the second row follow the sequence +6, +8.In the third row, the first letter G moves 7 steps forward to give the second letter N.Clearly, the missing letter will be 9 steps ahead of N i.e. W.

The numbers in the first row form a series 12, 22, 32.So, missing number in the first row = 42 = 16.The number in the second row from the series, 1, 2, 3, 4.The number in the third row from the series 2, 4, 6.So, missing number in the third row = 6 + 2 = 8.